You'd certainly learn things by using manual machines, getting a realistic idea of how fast to cut, what chips should look like if things are going well, and how to break up a job into a series of tasks for one machine or another. But if you're capable of making accurate CAD drawings and models, you'd be a lot more productive if you went the CNC route. Old Craftsman tools are not what I'd recommend; they weren't really the greatest when they were new, and once they've been abused for a while they might need more restoration work than they're worth. But Sherline makes manual as well as CNC versions of their lathes and mills, and they are high-quality tools. If your projects are small enough to fit their work envelopes, they would be a good machines to start learning about metal machining on. You can find out more about them on my site, under "Production".